title: Biosynthesis of 7-deazaguanosine-modified tRNA nucleosides: a new role for GTP cyclohydrolase I.
abstract: Queuosine (Q) and archaeosine (G(+)) are hypermodified ribonucleosides found in tRNA. Q is present in the anticodon region of tRNA(GUN) in Eukarya and Bacteria, while G(+) is found at position 15 in the D-loop of archaeal tRNA. Prokaryotes produce these 7-deazaguanosine derivatives de novo from GTP through the 7-cyano-7-deazaguanine (pre-Q(0)) intermediate, but mammals import the free base, queuine, obtained from the diet or the intestinal flora. By combining the results of comparative genomic analysis with those of genetic studies, we show that the first enzyme of the folate pathway, GTP cyclohydrolase I (GCYH-I), encoded in Escherichia coli by folE, is also the first enzyme of pre-Q(0) biosynthesis in both prokaryotic kingdoms. Indeed, tRNA extracted from an E. coli DeltafolE strain is devoid of Q and the deficiency is complemented by expressing GCYH-I-encoding genes from different bacterial or archaeal origins. In a similar fashion, tRNA extracted from a Haloferax volcanii strain carrying a deletion of the GCYH-I-encoding gene contains only traces of G(+). These results link the production of a tRNA-modified base to primary metabolism and further clarify the biosynthetic pathway for these complex modified nucleosides.
authors.affiliation: Department of Microbiology, University of Florida, Gainesville, FL 32611-0700, USA.
authors.forename: Gabriella
authors.initials: G
authors.lastname: Phillips
authors.forename: Basma
authors.initials: B
authors.lastname: El Yacoubi
authors.forename: Benjamin
authors.initials: B
authors.lastname: Lyons
authors.forename: Sophie
authors.initials: S
authors.lastname: Alvarez
authors.forename: Dirk
authors.initials: D
authors.lastname: Iwata-Reuyl
authors.forename: Valérie
authors.initials: V
authors.lastname: de Crécy-Lagard
mesh_terms: D016000:Cluster Analysis; D055028:Comparative Genomic Hybridization; D019295:Computational Biology; D004926:Escherichia coli / Q000201:enzymology / Q000235:genetics*; D029968:Escherichia coli Proteins / Q000235:genetics / Q000378:metabolism*; D006136:GTP Cyclohydrolase / Q000235:genetics / Q000378:metabolism*; D006151:Guanosine / Q000031:analogs & derivatives* / Q000096:biosynthesis; D019622:Haloferax volcanii / Q000201:enzymology / Q000235:genetics; D009704:Nucleoside Q / Q000096:biosynthesis; D010802:Phylogeny; D012329:RNA, Bacterial / Q000096:biosynthesis; D012343:RNA, Transfer / Q000096:biosynthesis*
chemical_list: D029968:Escherichia coli Proteins; D012329:RNA, Bacterial; D006151:Guanosine; C081066:archaeosine; D009704:Nucleoside Q; C068218:7-deazaguanosine; D012343:RNA, Transfer; D006136:GTP Cyclohydrolase